Definitions for "Interstitial Ads"
Interstitial ads are ads that appear between two content pages. If a user is on content page A and clicks on a hyperlink to go to content page B, the Interstitial page will appear after the user clicks on page A, before the user is moved to content page B.
Interstitials are ads that appear as a user moves between pages, either within a site or when the visitor leaves. They often are in the form of pop-up ads. Examples include subscription forms when you leave a publishing site.
An ad that loads in a small, separate browser window while you are waiting for a web page to load. There are two types of interstitial ads, the pop-up and the inline. Most Internet users consider interstitials to be very annoying.